Chemical-mechanical planarization is an enabling technology for the manufacturing of integrated circuits. Integrated circuits are generally mass produced by fabricating thousands of identical circuit patterns on a single semiconductor wafer and subsequently dividing them into identical die or chips. Semiconductor wafers are generally made of silicon. To produce the integrated circuit many process steps well known in the art are used to modify, remove, and deposit material onto the semiconductor wafer. These steps of deposition or removal are frequently followed by chemical-mechanical planarization (CMP). CMP is the process of planarizing or polishing a surface by the combination of chemical and mechanical forces. The CMP process enables the integrated circuit manufacturing by minimizing barriers to multilayer formation and metallization, as well as to smooth, flatten, and clean the surface.
One example of the CMP process involves holding a semiconductor substrate, such as a wafer, against a rotating polishing pad under controlled downward pressure. A polishing slurry is then deposited onto the polishing pad and contacts the substrate. The polishing slurry typically contains at least two components: chemical reactants and abrasive particles. The chemical reactants are typically simple complexing agents or oxidizers, depending on the materials to be polished, and acids or bases to control the pH. The abrasive particles are usually metal oxides and generally serve to mechanically abrade the surface, but can also contribute to the chemical action at the substrate surface.
The prior art has recognized the need for improved abrasive particles. Surface modified abrasives using organic silanes have been reported for achieving higher polishing rates and reducing agglomeration in the slurry (see for example U.S. Pat. No. 6,592,776 and U.S. Pat. No. 6,582,623). Another problem with abrasive particles is that they can stick to the polished substrate surface, resulting in contamination. This particle contamination can be difficult to wash away from the wafer and leads to higher defectivity and thus lowered yields in the integrated circuit manufacturing. There, thus, exits a need in the art for improved abrasive particles that have excellent polishing properties and result in low defectivity to the product.